Abstract
Breakdown strength, DC resistivity, permittivity and loss of thermally sprayed alumina coatings were studied at various temperatures and relative humidities. The studied coatings were sprayed by utilizing three different spray techniques: flame, high-velocity oxygen fuel (HVOF) and plasma spraying. Breakdown behavior of HVOF sprayed alumina were studied up to very high temperatures (800 °C). At 20–180°C, no significant trend could be seen in the breakdown strength of HVOF and plasma sprayed alumina coatings. The breakdown strength of alumina coatings decreased gradually from 300 to 800 °C reaching a value which was only 14% of the breakdown strength measured at 20 °C/RH 20%. Increasing humidity (from 20 to 90%) decreased the DC resistivity of the alumina coatings five orders of magnitude. Correspondingly, permittivity and losses increased with the humidity; in most cases with a notable contribution due to DC conduction. The material behavior may be linked to the microstructure of coatings consisting of amorphous and crystalline regions with interfaces in between. Moreover, the alumina coatings exhibited notable amount of highly hygroscopic γ-phase which also affected the moisture sensitivity of the coatings.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: IEEE Transactions on Dielectrics and Electrical Insulation
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
